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(No Model.) 3 Sheets-Sheet 1.

W. A. ANTHONY.

ELEOTRIO INDICATOR.

No. 387,131. Patented July 31, 1888.

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W. A. ANTHONY.

ELECTRIC INDICATOR.

No. 887,131. Patented July 31, 1888.

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ELECTRIC INDICATOR.

Patented July 31, 1888.

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W'ILLIAM A. ANTHONY, OF MANCHESTER, CONNECTICUT, ASSIGNOR TC THE MATHERELECTRIC COMPANY, OF SAME PLACE.

ELECTREC INDICATOR.

SPECIFICATION forming part of Letters Patent No. 387,131, dated July 31,1888.

Application filed March 26, 1888.

To all whom it may concern:

Be it known that 1, WILLIAM A. ANTHONY, of- Manchester, in Hartfordcounty, Connecticut, have invented certain new and useful Im provementsin Electric Indicators, which improvements are described in thefollowing specification, and are illustrated by the accompanyingdrawings.

The invention relates to that class of elec- 1o trio indicators in whicha stationary helix and a movable helix of insulated wire, forming partof an electric circuit, interact upon each other to produce in suchmovable helix those movements of partial revolution which indicatechanges of current or electro motive force.

The object of the invention is to cause equal electric changes to beindicated by equal movements throughout the whole range of such aninstrument. To accomplish this result my invention opposes to thedirecting power of the stationary and movable helices the force of aweight which is applied to the movable helix by means of a flexibleconnection run- 2 ning over a curved surface.

The best method in which I have contemplated applying the principle ofmy invention is illustrated in the drawings.

Figure 1 is a central vertical section of a 0 potential indicator, whichis constructed in accordance with my invention for the purpose ofindicating a normal difference of potential of one hundred and twentyvolts, and other differences of potential not more than fourteen 5 voltsgreater or less than one hundred and twenty volts. Fig. 2 is a centralvertical section of the same in a plane which is at right angles withthe sectional plane of Fig. 1. Fig. 3 is a plan of the same, exceptingthe graduated scale. Figs. 4: and 5 are details showing a modifiedconstruction.

The numeral 1 denotes a stationary helix of insulated fine wire, whichis wound upon a hollow brass spool, 2. This spool, which is short and oflarge internal diameter, is pro vided at the bottom with aninwardly-projecting annular brass ilange, 3, and is supported in ahorizontal position by metallic standards 4., which rise from the top ofbase 5,

and are attached to flange 3 by screws. Upon Serial No. 268,502. (Nomodel.)

this flange is mounted an inwardly projecting horizontal bracket, 6,having two arms for the support of thenioving parts of the indicator.

Two small cups, 7 and 8, containing mercury,

are secured to flange 3 on opposite sides of bracket 6. Cup 7 isinsulated and cup 8 is not insulated from said flange. An archedscaleplate, 9, which is held up by standards 10,,spans the top of spool2. This plate is graduated uniformly from end to end, and reads througha predetermined range of fourteen volts, more or less, in each directionfrom the central reading of one hundred and twenty volts, the latterbeing the normal electromotive force of the circuit whose changes ofpotential are .to be observed. A similar but smaller helix, 11, is woundupon a similar spool of insulating material, 12. Spool 12 is providedwith a central cross-bar carrying a knife, 13, whose edge occupies adiametrically 7o horizontal position in the annular helix and spool 11and 12. Knife-edge 13, resting in a V-groove across the two arms ofbracket 6, supports the moving parts of the instrument. On the loweredge of spool 12 is an adj ustable weight, 14, whereby the center ofgravity of said spool and its attachments is located slightly below theline of knife-edge 13. On the upper edge of spool 12 is aradially-directed pointer, 15. Spool 12 also carries two contact platesor hangers, 16 and 17, of amalgamated copper, which are attached tosaid. spool by brackets 32 and 33, and hang down into cups 7 and 8,respectively. Bracket 32 holds a circular plate or disk, 18, which is atright angles with the line of knife-edge 13 produced, and has a groovedperiphery on which runs a silk thread, 19. One end of this thread isfastened to disk 18, and the other end of the same is fastened toadependent weight, 20. Base 5, which is a wooden box having airholes 21,contains an artificial resistance, 22, consisting of German silver,carbon, or other material of low or negative temperature co efficient.Resistance 22, being in the form of wire or filament, is freelydispersed in base 1 to avoid heating. Binding-posts 23 and 24 are theterminals of the indicator, and wires 25 and 26 are a shunt to the maincircuit, whose potential is to be indicated. One end :00

of the wire composing helix 1 is soldered to spool 2, and the other endof the same is connected to post 23 by wire 27. Helix 11 is connectedwith bracket 33 by wire 28 and with bracket 32 by wire 29. Resistance 22is connected with cup 7 by wire 30 and with binding-post 24. by wire 31.In short, said helices and said resistance are connected in series.

The remaining features of construction of this potential indicator willsufficiently appear from the drawings and from the mode of operation,which is now to be described.

The mode of operation of thisinstrument is similar to that of thewell-known iVeber dynamometer. When no difference ofpotential, or nodifference exceeding the minimum indication of the instrument, existsbetween terminals 23 and 24, pointer 15 stands in the positioninwhichitisshownin Fig.1,andisstopped from greater deflection from avertical position. Vhen the difference of potential between terminals 23and 24 stands at the normal limit of one hundred and twenty volts,pointer 15 is held in a vertical position, as in Fig. 2. The currenttakes its course from terminal 23 successively through wire 27, helix 1,spool 2, flange 3, cup and contents 8, plate 17, bracket 33, wire 28,helix 11, wire 29, bracket 32, plate 16, cup and contents 7, wire 30,resistance 22, and wire 31 to terminal 24. Resistance 22 preventshelices l and 11 from becoming so much heated as to present anyconsiderable variations in resistance, and easily radiates heat from itsown snrface into the surrounding air. A condition of thermal equilibriumis accordingly reached with little delay. If the difference of potentialwhich is to be observed rises above or falls below one hundred andtwenty volts, the change within a total range of twentyeight volts isindicated to the eye of the observer by a proportionatedeflection ofpointerlobeforescale-plate 9. This deflection results from the directingpower of helices 1 and 11, the opposing force of weight 20, and therelative position of the axis ofsupport and center of gravity ofhelix 11and its attachments. The directing power of said helices is variablewith the relative positions which they occupy and the eleetro-motiveforce with which they are supplied. Equal changes in electro-motiveforce affect the directing power of said helices unequally for differentparts of the scale. The opposing force of weight 20 is constant in allpositions within the range of the instrument. The effect which is due tothe relative positions of the axis and center of gravity of helix 11 andits attachments varies according to the side of the angle at whichpointer 15 is deflected from the perpendicular. By correctly determiningthe necessary curvature of plate 18 the described forces can be balancedagainst each other in such a manner that equal changes of potential willproduce equal movements of the pointer throughout the whole range of theinsustaining weight 20, takes the place of the I above-describedcircular disk, which is indicated by the same numeral 18. This plate hassuch a peripheral curvature that the moment of weight varies inverselyas the directing force of the interacting helices 1 and l1. By varyingthe curvature of plate 18, or by changing the location of said platerelatively to its axis of oscillation, or by a combination of thesemethods, the moment of weight 20 may be rendered constant or caused tovary in accordance with any desired law.

The foregoing statement of the construction and mode of operation of myinvention has special reference to the construction and operation of thesame as a potential indicator for constant-potential circuits. \Vhenconstructed and used as a current-indicator for constant-currentcircuits, helices 1 and 11 are formed of coarse wire, resistance 22 isomitted, plate 9 is graduated to indicate changes of current, and theinstrument takes all or a known fractional part of the current of thecircuit to which it is applied. In that case wires 25 and 26 are a partof the main circuit, whose current changes are to be indicated.

Such being the construction and operation of my invention, I claim- 1.In an instrument for indicating or measuring current or potential, anelectric conduetor which is pivoted in a magnetic field, and a curvedplate or lever which is attached to said pivoted conductor, incombination with a weight and a flexible connection whereby said weightis suspended from said curved lever, substantially as and for thepurpose specificd.

2. In an electric indicator, means for producing a magnetic field, andan oscillating conduetor which is located in said field and is providedwith an attachment having a curved surface, in combination with a cordrunning upon said curved surface and aweight which is suspended by saidcord, substantially as and for the purpose specified.

3. A stationary helix, an oscillating helix, and a plate which has aperipheral curvature and is attached to said oscillating helix, incombination with a weight and a flexible connection by which said weightis suspended from said plate, substantially as and for the purposespecified.

4. A stationary helix and an oscillating strument, and in the describedindicator this I helix which is pivoted therein and is proattached tosaid oscillating helix, a weight, graduated scale, a plate which has aperiphand 'a thread by which said weight is suseral curvature and isattached to said osoillatpended from said plate, substantially as anding helix, a weight, and a thread by which for the purpose specified. I5said weight is suspended from said plate, sub- In testimony whereof Ihereunto set my hand stantially as and for the purpose specified. in thepresence of two witnesses.

5. A stationary helix and a movable helix of copper wire, and anartificial resistance of WILLIAM ANTHDNY' low or negative temperature,coefficient, all connected in series, in combination with a plate whichhas a peripheral curvature andis vided with a pointer, in combinationwith a lVitnesses:

WILLARD EDDY, EBEN E. SMITH.

